Sternal osteotomy guide and sternal fixation system

ABSTRACT

Systems and methods are described for a sternal osteotomy guide and sternal fixation system.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Patent Application No. 62/103,257, filed on Jan. 14, 2015, the content of which is herein incorporated by reference into the subject application.

BACKGROUND OF THE INVENTION

Throughout this application various publications are referred to in superscripts. Full citations for these references may be found at the end of the specification before the claims. The disclosures of these publications are hereby incorporated by reference in their entireties into the subject application to more fully describe the art to which the subject application pertains.

Midline axial sternotomy, first described by Milton in 1887 and reintroduced by Julian and Associates in 1957,1 is the most frequently performed osteotomy worldwide², and is the preferred technique for exposure of the heart and great vessels. Despite its advantages, sternal wound complications may occur. Sternal dehiscence can occur in 0.2% to 5% of patients due to poor wound healing and surgery related factors.³⁻⁵

Sternal dehiscence and deep sternal wound infection (DSWI) are post-sternotomy wound complications that result in significant morbidity and mortality as well as prolonged hospital stay and increased cost to patients who undergo cardiac surgery. The reported prevalence of this complication ranges from 1-5% with reported associated mortality of up to 25%.^(6,7) While relatively rare, when they do occur these complications can be severe and costly.

Numerous preoperative and operative risk factors have been identified as predictors of DSWI following cardiac surgery. These include obesity, diabetes mellitus, chronic obstructive pulmonary disease, smoking, steroid use, New York Heart Association functional class IV, osteoporosis, immunosuppression, and previous sternotomy. Operative risk factors include bilateral internal mammary artery harvest, prolonged cardiopulmonary bypass time, and transverse sternal fractures.⁸ Additionally, patients with multiple known risk factors or off midline sternotomy have been identified as high risk for sternal dehiscence.^(9,10)

Primary reinforcement, an alternative technique to traditional closure by wire circlage, has been advocated for high-risk patients. Primary sternal plating, stainless steel coils, cables, or recently, a sternal synthesis device are cited as increasing sternal stability and thereby potentially reducing wound infection rates.^(9,10) The decision to employ alternative techniques and materials depends on the surgeon's ability to identify high risk patients who would benefit from such primary reinforcement. However, alternative techniques to prevent faulty sternotomy have not been thoroughly addressed in the literature. There are no identified patents that address the issue of asymmetric osteotomy of the sternum with a cutting guide. The present invention addresses the need for improved treatment procedures and apparatus.

SUMMARY OF THE INVENTION

Systems and methods are described for a sternal osteotomy guide and sternal fixation system. Preferably, a sternal fixation system includes one or more non-bioresorable intra-sternal shims, one or more tie members, one or more pairs of brackets, and, optionally, a ratchet gun. Preferably, the shim is configured to be placed between sternal halves and to provide anteroposterior stability once the sternal halves have been pulled together. Preferably, the shim has a relatively thicker or wider center portion than its lateral sides. Preferably, an elongated tie member is attached to or passes through the shim. Preferably, the tie has a first end portion that includes a first gear rack on a surface thereof, and a second end portion that includes a second gear rack on a surface thereof. Preferably, teeth forming the first and second gear racks slope in opposing directions. Preferably, the pair of brackets are configured to distribute pressure at a cortical interface thereof and each pair includes a central ratcheting mechanism operable to interface with the first or second tie gear racks. Preferably, the ratchet gun provides uniform tightening of the pair of brackets.

Preferably, the sternal cutting guide comprises a cutting slot adjustable in the cranio-caudal direction of the sternum, wherein the cutting slot allows passage of a sternal saw; hooks for fixing the cutting guide to a patient; and optionally, drilling eyelets for drilling at multiple positions on both sides of the sternum.

The devices described herein can be used in methods of fixating the sternum of a patient following sternal osteotomy where the methods include creating a midline sternal osteotomy; drilling holes in the anterior sternal cortex for passage of shim ties; placing one or more non-bioresorbable intra-sternal shims between halves of the cut sternum; passing needles attached to the shim ties from intramedullary to extracortical portions of the sternum; removing the needles from the shim ties leaving a portion of the shim tie protruding from the sternum; positioning on each side of the sternum one of a pair of brackets on the ties for each shim; and tightening each pair of brackets using the ratchet gun, thereby fixating the sternum of the patient following sternal osteotomy.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1. Illustration of a front view of a sternum. The sternum osteotomy guide can be positioned on the sternum to osteotomize at the midline (along the dotted line).

FIG. 2. Illustration of an example of a sternal osteotomy guide placed on the sternum to facilitate osteotomization of the sterum at the midline.

FIG. 3. Illustration of an example of a top view of an adjustable body of a cutting slot of a sternal osteotomy guide.

FIG. 4. Illustration of an example of a side view of a sternum osteotomy guide positioned on a sternum.

FIG. 5. Illustration of an example of an isometric view of a sternum osteotomy guide positioned on a sternum.

FIG. 6. Illustration of an example of a front view of a completed sternal osteotomy with the sternal osteotomy guide removed.

FIG. 7. Illustration of an example of a front view of a sternal fixation system showing shims, ties and brackets applied.

FIG. 8. Illustration of an example of a front view of a sternal fixation system showing shims, ties and brackets placed in multiple locations on the sternum.

FIG. 9. Illustration of an example of a side view of a ratchet gun that can be used to attach brackets to ties at a uniform tension.

FIG. 10. Illustration of an example of an isometric view of a sternum closed with a shim placed inside the sternum, brackets on lateral sides of the sternum and ties tightened.

FIG. 11. Illustration of an example of a shim centered in the intramedullary canal of a sternum.

FIG. 12. Illustration of an example of a front view of a sternum closed with 5 shims placed on the inside of the sternum, brackets on lateral sides of the sternum and ties tightened.

FIG. 13. Illustration of an example of a cross-sectional view of a sternum closed with a shim placed inside the sternum, brackets on lateral sides of the sternum and ties tightened.

FIG. 14. Illustration of an example of a top view of a shim having a three dimensional shape that is thicker in its middle than edges and having attachment sites for ties.

FIG. 15. Illustration of an example of an isometric view of a shim that may be solid, porous or meshed.

DETAILED DESCRIPTION OF THE INVENTION

Systems and methods are described for a sternal osteotomy guide and sternal fixation system. The purpose of the sternal osteotomy guide and sternal fixation system is to rigidly fix the hemi-sternal bones, providing both transverse compression and anteroposterior stability. The fixation method must allow rapid re-entry into the chest in the event of a post-operative, intra-thoracic catastrophe. Total time for creation of the midline sternotomy and closure using the most commonly employed current methods is approximately 10-15 minutes. Any technique that replaces these methods must be as fast or faster, relatively inexpensive, and provide fixation at least as efficiently. An ideal solution would not require the use of devices or techniques overtly foreign to the cardiac surgeon. An ideal method would provide the surgeon with uniformity of compression and minimal foreign material, case-to-case.

The sternal fixation system described in this application addresses major points of weakness in the current methods. First, a reusable, adjustable cutting guide is used to create a midline osteotomy, thereby reducing the risk of DSWI due to asymmetric osteotomy. This same cutting guide is used to pre-drill the holes in the anterior sternal cortex for passage of the shim ties at the completion of the procedure. Once the procedure is complete, needles attached to the shim ties are passed from intramedullary to extracortical and then cut off, leaving only the zip-tie portion of the shim tie sticking out of the antero-lateral cortex of the sternum. A sternal bracket is then slid down, flush to the sternum on the non-surgeon side of the table. The surgeon then uses a calibrated gun to fix a second bracket also flush to the sternum on his or her side of the table. The shims through which the ties pass are intra-sternal.

Preferably, the sternal fixation system includes a non-bioresorbable intra-sternal shim, a tie member, a pair of brackets and, optionally, a ratchet gun. The shim can be configured to be placed between sternal halves and to provide anteroposterior stability once the sternal halves have been pulled together. The shim can have a relatively thicker center portion than its lateral sides. The tie member can be attached to or passed through the shim. A first end portion of the tie member can include a first integrated gear rack on a surface thereof. A second end portion of the tie member can include a second integrated gear rack on a surface thereof. Preferably, the teeth forming the first and second integrated gear racks slope in opposing directions. Preferably, brackets are configured in pairs to distribute pressure at a cortical sternal interface thereof, and each pair includes a central ratcheting mechanism operable to interface with the first integrated gear rack or the second integrated gear rack. Preferably, the ratchet gun provides uniform tightening of the pair of brackets.

Preferred, non-limiting features of the preferred sternal cutting guide and sternal fixation system are described in the following.

Sternal Cutting Guide

-   -   Made of stainless steel or titanium material     -   Reusable     -   Typical use for adults (16+)     -   Also available in pediatric sizes     -   Comes in small, medium and large sizes (optional)     -   Made up of the following components:     -   1. Cutting Slot         -   a. Allows passage of sternal saw-adjustable kerfs         -   b. Adjustable in the cranio-caudal direction         -   c. Flat or slightly curved in the cranio-caudal direction         -   d. Has tension in adjustable slot         -   e. Release mechanism for tension         -   f. Mechanism for determining midline position relative to             sternum         -   g. Parallel membranes at standard or variable width to form             cutting slot     -   2. Hooks         -   a. Fix beneath sternal notch and at xiphoid.         -   b. Shaped in “Y” pattern to allow for insertion/exiting of             traditional sternal saw     -   3. Drilling Eyelets (optional)         -   a. Bilateral         -   b. 4-8 pairs of evenly spaced eyelets at same level on             either side of sternum         -   c. Angled to drill through single cortex of sternum (allow             unicortical penetration)         -   d. Come out from side of cutting slot         -   e. Designed to place hole at multiple distances lateral from             osteotomy site (e.g., 1, 1.5, 2 cm, etc.)         -   f. Left and Right eyelets are parallel         -   g. Provides drill stop to disallow bicortical penetration         -   h. Some holes positioned on top slider and some on bottom             slider (e.g., 4 on top, 4 on bottom)         -   i. Guide position, angulation and depth of hole.

Sternal Fixation System

-   -   Made of multiple materials     -   Not reusable     -   Typical use for adults (16+)     -   Available for pediatric patients     -   Comes in small, medium and large sizes (optional)     -   Made up of the following components:     -   1. Ties         -   a. Made of plastic (e.g., polyether ether ketone (PEEK)) or             stainless steel         -   b. Have zip tie-like ratcheting system         -   c. Zip ties are in opposing direction on opposite sides of             shim         -   d. Attached to cutting needle on both ends         -   e. Length approximately 20-45 cm         -   f. Attach to or pass through shim     -   2. Shims         -   a. Non bioresorbable         -   b. Titanium impregnated (with biological/bioactive             substance), Titan Mesh or non-impregnated porous             polyethylene (MEDPOR®)-like material         -   c. Shim allowed to slide along or fixed to tie         -   d. Shim is three-dimensionally thinner on lateral sides,             thicker in center         -   e. Come in small, medium and large sizes         -   f. If tie is passing through shim, then shim will have             central slot or tunnel         -   g. Microbarbs in opposing directions to encourage better             fixation inside sternal medullary canal (optional)     -   3. Brackets:         -   a. Central ratcheting mechanism (CRM) Tightened via rachet             gun or by hand         -   b. Buttons with mechanism to attach to zip ties         -   c. 2 deformable metal tabs (alternate to option b)             -   i. Low profile             -   ii. Malleable to make them flush with sternal                 border—whether it is on the lateral or anterior surface                 of the sternum     -   4. Ratchet Gun (optional)         -   a. Load variable         -   b. Similar to zip tie gun         -   c. Reusable or non reusable         -   d. Used to tighten brackets on tie to sternum         -   e. Provides standard tightening every time         -   f. Stores and loads brackets (optional)         -   g. Angled and narrowed snout (optional)         -   h. Real time tension display     -   5. Disassembling Tool (optional)         -   a. Cutting mechanism to unfasten brackets from ties         -   b. Rongeur-like cutting tool to capture unfastened brackets.

Asymmetric osteotomy of the sternum is a major cause of DSWI (deep sternal wound infection) which, in turn, is a major cause of post-cardiac surgery morbidity and mortality as well as cost to the health care system. Using the sternal osteotomy guide to guide a midline osteotomy, the complications from DSWI should decrease. The present systems and methods include the following advantages:

-   -   Monocortical drill holes provide access for placement of a fast,         simple, transversely oriented fixation system     -   Fast, cheap, non-bioreactive, allows for rapid re-entry into         chest, uniform closure pressure, A-P (anteroposterior) as well         as transverse compression     -   Ties—Fast, cheap, non-reactive     -   Shims—Provide A-P stability of sternum     -   Brackets—Distribute pressure at cortical interface; decrease         likelihood of cut-through     -   Ratchet Gun—Provides uniform tightening.

REFERENCES

-   1. Dalton M L, Connally S R, Sealy W C. Julian's reintroduction of     Milton's operation. Ann Thorac Surg 1992; 53:532-533. -   2. Raman J, Song D H, Bolotin G, Jeevanandam V. Sternal closure with     titanium plate fixation—a paradigm shift in preventing     mediastinitis. Interact Cardiovasc Thorac Surg. 2006; 5:336-339. -   3. Casha A R., Yang L, Kay P H, Saleh M. Cooper G J. A biomechanical     study of median sternotomy closure technique. Eur J Cardiothorac     Surg 1999; 15:365-9. -   4. Olbrecht V A, Barreiro C J, Bonde P N, Williams J A, Baumgartner     W A, Gott V L, Conte J V. Clinical outcomes of noninfectious sternal     dehiscence after median sternotomy. Ann Thorac Surg. 2006;     82:902-907. -   5. Robicsek F, Fokin A, Cook J, Bhatia D. Sternal instability after     midline sternotomy. Thorac Cardiovasc Surg 2000; 48:1-8. -   6. Gummert J F, Barten M J, Hans C, Kluge M, Doll N, Walther T,     Hentschel B, Schmitt D V, Mohr F W, Diegeler A. Mediastinitis and     cardiac surgery—an updated risk factor analysis in 10,373     consecutive adult patients. Thorac Cardiovasc Surg 2002; 50:87-91. -   7. Sachithanandan A, Nanjaiah P, Nightingale P, Wilson I, Graham T,     Rooney S, Keogh B, Pagano D. Deep sternal wound infection requiring     revision surgery: impact on mid-term survival following cardiac     surgery. Eur J Cardiothorac Surg 2008; 33:673-678. -   8. Snyder C W, Graham L A, Byers R E, Holman W L. Primary sternal     plating to prevent sternal wound complications after cardiac     surgery: early experience and patterns of failure. Interact     Cardiovasc Thorac Surg. 2009; 5:763-6. -   9. Zeitani J, Penta de Peppo A, Moscarelli M, Guerrieri Wolf L,     Scafuri A, Nardi P, Nanni F, Di Marzio E, De Vico P, Chiariello L.     Influence of sternal size and inadvertent paramedian sternotomy on     stability of the closure site: a clinical and mechanical study. J     Thorac Cardiovasc Surg. 2006; 132:38-42. -   10. Zeitani J, Penta de Peppo A, Bianco A, Nanni F, Scafuri A,     Bertoldo F, Salvati A, Nardella S, Chiariello L. Performance of a     novel sternal synthesis device after median and faulty sternotomy:     mechanical test and early clinical experience. Ann Thorac Surg.     2008;85(1):287-93. 

What is claimed is:
 1. A sternal fixation system comprising: one or more non-bioresorbable intra-sternal shims configured to be placed between sternal halves and to provide anteroposterior stability once the sternal halves have been pulled together, each shim having a relatively thicker center portion than its lateral sides; one or more tie members attached to or passing through each shim, the tie member having a first end portion and a second end portion and including a first integrated gear rack on a surface of the first end portion and a second integrated gear rack on a surface of the second end portion, wherein the first integrated gear rack is formed by a first plurality of teeth that slope in a first direction and the second integrated gear rack is formed by a second plurality of teeth that slope in a second direction opposing the first direction; and one or more pairs of brackets configured to distribute pressure at a cortical interface thereof and each pair having a central ratcheting mechanism operable to interface with the first integrated gear rack or the second integrated gear rack.
 2. The sternal fixation system of claim 1, wherein one or more shims are solid, porous or meshed.
 3. The sternal fixation system of claim 1, wherein one or more shims comprise titanium impregnated with a biological or bioactive substance, titanium mesh or non-impregnated porous polyethylene.
 4. The sternal fixation system of claim 1, wherein one or more shims have a triangular shape on one or more sides of the tie member.
 5. The sternal fixation system of claim 1, wherein the ties comprise polyether ether ketone or stainless steel.
 6. The sternal fixation system of claim 1, further comprising a ratchet gun to provide uniform tightening of pairs of brackets.
 7. The sternal fixation system of claim 6, wherein the ratchet gun attaches brackets to ties at a uniform tension.
 8. The sternal fixation system of claim 1, further comprising a sternal cutting guide.
 9. The sternal fixation system of claim 1, further comprising a disassembling tool comprising a cutting mechanism to unfasten brackets from ties and/or a rongeur-like cutting tool to capture unfastened brackets.
 10. A sternal cutting guide comprising a cutting slot adjustable in the cranio-caudal direction of the sternum, wherein the cutting slot allows passage of a sternal saw; and hooks for fixing the cutting guide to a patient.
 11. The sternal cutting guide of claim 10, wherein the guide comprises stainless steel and/or titanium.
 12. The sternal cutting guide of claim 10, wherein the cutting slot comprises one or more of flat or slight curvature in the cranio-caudal direction, tension in the adjustable slot and a release mechanism for tension, a mechanism for determining midline position relative to the sternum, and parallel membranes at standard or variable width to form the cutting slot.
 13. The sternal cutting guide of claim 10, wherein the hooks fix beneath the sternal notch and at the xiphoid of a patient, and the hooks are shaped in a “Y” pattern to allow access of a sternal saw to the cutting slot.
 14. The sternal cutting guide of claim 10, wherein the guide further comprises drilling eyelets for drilling at multiple positions on both sides of the sternum.
 15. A method of fixating the sternum of a patient following sternal osteotomy using the sternal fixation system of claim 1, the method comprising: creating a midline sternal osteotomy; drilling holes in the anterior sternal cortex for passage of shim ties; placing one or more non-bioresorbable intra-sternal shims between halves of the cut sternum; passing needles attached to the shim ties from intramedullary to extracortical portions of the sternum; removing the needles from the shim ties leaving a portion of the shim tie protruding from the sternum; positioning on each side of the sternum one of a pair of brackets on the ties for each shim; and tightening each pair of brackets using a ratchet gun, thereby fixating the sternum of the patient following sternal osteotomy.
 16. The method of claim 15, wherein an adjustable cutting guide is used to create the midline sternal osteotomy and/or drill holes in the anterior sternal cortex. 